The invention relates to a method for manufacturing oligomeric and/or polymeric precursors of polyoxazoles and polythiazoles, as well as the use of these precursors.
Precursors of polyoxazoles and polythiazoles are known (see, for instance: E. Behr, "High-Temperature-Stable Plastics", Carl Hanser Publishers, Munich, 1969, pages 99 to 102). They are made from dihydroxy diamines or dimercapto diamines and dicarboxylic acid derivatives, especially acid chlorides. By annealing (at temperatures between 220.degree. and 500.degree. C. or at approximately 400.degree. C.), these precursors can be converted into polyoxazoles or polythiazoles.
Polyoxazoles and polythiazoles can be used, for instance, in the rastering of input screens for x-ray image amplifiers and particularly in microelectronics, and specifically as etching-resistant protection and insulating layers since they have high thermal stability in air (up to approximately 520.degree. C.) and excellent chemical resistance to acids and bases. However, the requirements as to purity are very high in these applications in order to prevent corrosion phenomena in operation over extended periods of time. The strong cost pressure in the semi-conductor sector further compels the use of inexpensive materials and processes.
From U.S. Pat. No. 4,398,009, a method for manufacturing polyoxazole precursors is known, in which an aromatic and/or heterocyclic dihydroxydiamino compound is reacted with a dicarboxylic acid chloride or ester to form a hydroxyl group-containing polycondensation product and then an olefinically unsaturated monoepoxide is added to this polycondensation product. In this manner, radiation-reactive polyoxazole precursors are obtained, i.e., these compounds can be cross-linked by radiation and thus converted into highly heat-resistant polymers (see in this connection U.S. Pat. No. 4,332,883).
In addition to the foregoing resists (these are so-called negative resists), heat-resistant positive resists with a base of polyoxazole precursors are known. These positive resists have polyoxazole precursors in the form of polycondensation products of dihydroxydiamino compounds and dicarboxylic acid chlorides or esters as well as light-sensitive diazoquinones (U.S. Pat. No. 4,339,521). In the polyoxazole and polythiazole precursors known so far, however, the preparation with high purity poses problems if acid chlorides are used, and is expensive. For, the known synthesis methods are very expensive especially because extensive purification operations are required to obtain a low chloride content. On the other hand, predominantly only low-molecular compounds are produced if esters are used.
It is an object of the invention to develop a method which permits a simple production of oligomeric and/or polymeric polyoxazole and polythiazole precursors of high purity, i.e., of precursors which, in particular, are free of chloride.